Nonwoven abrasive article and method of making the same

ABSTRACT

A nonwoven abrasive article includes a lofty open nonwoven fiber web comprising entangled fibers; and abrasive platelets secured to the entangled fibers by at least one binder material. A majority of the abrasive platelets are respectively bonded in an edge-wise manner to at least one of the entangled fibers. Methods of making the nonwoven abrasive article and converted forms, including a convolute abrasive wheel, are also disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.15/555,910, filed Sep. 5, 2017, now allowed, which is a national stagefiling under 35 U.S.C. 371 of PCT/US2016/025024 filed Mar. 30, 2016,which claims the benefit of U.S. Provisional Application No. 62/147,369,filed Apr. 14, 2015 and U.S. Provisional Application No. 62/196,675,filed Jul. 24, 2015, the disclosure of which is incorporated byreference in its entirety herein.

TECHNICAL FIELD

The present disclosure broadly relates to nonwoven abrasive articles,and methods of their manufacture and use.

BACKGROUND

Nonwoven abrasive articles generally have a nonwoven web (e.g., a loftyopen fibrous nonwoven web), abrasive particles, and a binder material(commonly termed a “binder”) that bonds the fibers within the nonwovenweb to each other and secures the abrasive particles to the nonwovenweb. Examples of nonwoven abrasive articles include nonwoven abrasivehand pads and surface conditioning abrasive discs and belts such asthose marketed by 3M Company of Saint Paul, Minn. under the tradedesignation SCOTCH-BRITE.

Nonwoven abrasive wheels are another type of nonwoven abrasive article.Examples of nonwoven abrasive wheels include convolute abrasive wheels(spirally wound nonwoven abrasive web around a core) and unitizedabrasive wheels (one or more individual discs of nonwoven abrasive webformed into a stack). Nonwoven abrasive wheels are also available from3M Company of Saint Paul, Minn. under the trade designationSCOTCH-BRITE.

In one manufacturing method, a nonwoven fiber web is coated with abinder precursor material. Next, abrasive particles are adhered to thebinder precursor material, which is then cured to secure the abrasiveparticles to the fiber web.

Historically, lofty, open, non-woven abrasive articles have been madeusing a variety of coating techniques. For example, in the U.S. Pat. No.2,958,593 (Hoover et al.), nonwoven abrasive articles were made by thespray application of a relatively dilute slurry comprising a solution ofa binder, solvent, and abrasive particles. In another method, theabrasive particles may be applied by a drop coating method as describedin PCT Internat. Publ. No. WO 2014/137972 A1 (Kaur et al.).

U.S. Pat. No. 6,017,831 (Beardsley et al.) describes yet another acoating technique in which a uniformly dispersed cloud of fine abrasiveparticles is deposited (preferably by settling due to gravity) ontobinder precursor-coated fibers. Use of electrostatic coating to orientabrasive particles and bond them to a lofty nonwoven material isdescribed in U.S. Pat. No. 7,393,371 (O'Gary et al.).

SUMMARY

Notwithstanding the above disclosure, the present inventors unexpectedlyfound that under suitable conditions, abrasive platelets can be coatedcontinuously along the fibers of the nonwoven fiber web such that theyare disposed as a single layer (preferably closely-packed), with theabrasive particles extending perpendicularly in all directions aroundthe fiber axis.

In a first aspect, the present disclosure provides a nonwoven abrasivearticle comprising:

a nonwoven abrasive article comprising:

-   -   a lofty open nonwoven fiber web comprising entangled fibers; and    -   abrasive platelets secured to the entangled fibers by at least        one binder material, and    -   wherein a majority of the abrasive platelets are respectively        bonded in an edge-wise manner to at least one of the entangled        fibers, respectively.

Nonwoven abrasive articles according to the present disclosure may havethe form of a hand pad, floor pad, surface conditioning pad, flap brush,disc, belt; or be converted into a unitized or convolute abrasive wheel.

In a second aspect, the present disclosure provides a method of makingan abrasive article, comprising the steps:

i) providing a lofty open nonwoven fiber web comprising a plurality ofentangled fibers;

ii) coating at least a portion of the lofty open nonwoven fiber web witha first curable binder precursor to provide a coated fiber web;

iii) electrostatically depositing a plurality of abrasive platelets onat least a portion of the first curable binder precursor; and

iv) at least partially curing the first curable binder precursor,wherein a majority of the abrasive platelets are each bonded in anedge-wise manner to at least one of the entangled fibers, respectively.

In certain preferred embodiments, the method further comprises coatingat least a portion of the first curable binder precursor and abrasiveplatelets with a second curable binder precursor, and at least partiallycuring the second binder precursor.

Unexpectedly and advantageously, nonwoven abrasive articles according tothe present disclosure exhibit superior abrading performance as comparedto conventional nonwoven abrasive articles typical of the abrasive art.

As used herein:

The term “bonded in an edge-wise manner” in reference to abrasiveplatelets bonded to fibers means that the abrasive platelets are bondedmainly by their peripheral edges to the fibers.

The term “closely-packed” in reference to abrasive platelets bonded tofibers means that a majority of the abrasive platelets (e.g., at least50 percent, at least 60 percent, or even at least 75 percent) are spacedapart from adjacent abrasive platelets by a distance of less than thewidths of the adjacent abrasive platelets.

The term “orthogonal” means forming an angle of from 75 degrees to 105degrees (preferably 80 degrees to 100 degrees, and more preferably 85degrees to 95 degrees).

The term “abrasive platelet” refers to an abrasive particle (whetherrandomly crushed, intentionally shaped and/or molded (e.g., a thintruncated triangular pyramid), or other) resembling a minute flattenedbody and/or flake that is characterized by a thickness that issubstantially less than the width and length. Abrasive plateletsgenerally have two opposed major sides defining the length and width ofthe abrasive platelet, and with the thickness disposed therebetween,joined along a peripheral edge that includes at least one line and/or atleast one surface. For example, the thickness may be less than ½, ⅓, ¼,⅕, ⅙, 1/7, ⅛, 1/9, or even less than 1/10 of the length and/or width.

The term “length” refers to the longest dimension of an object.

The term “width” refers to the longest dimension of an object that isperpendicular to the length.

The term “thickness” refers to the remaining dimension that isperpendicular to the length and the width.

Features and advantages of the present disclosure will be furtherunderstood upon consideration of the detailed description as well as theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of exemplary nonwoven abrasive article100.

FIG. 1B is an enlarged view of region 1B of nonwoven abrasive article100 shown in FIG. 1A.

FIG. 2 is a perspective view of exemplary convolute abrasive wheel 200.

FIG. 3 is a perspective view of exemplary unitized abrasive wheel 300.

FIGS. 4-15 are photomicrographs of nonwoven abrasive articles preparedin the Examples section hereinbelow.

Repeated use of reference characters in the specification and drawingsis intended to represent the same or analogous features or elements ofthe disclosure. It should be understood that numerous othermodifications and embodiments can be devised by those skilled in theart, which fall within the scope and spirit of the principles of thedisclosure. The figures may not be drawn to scale.

DETAILED DESCRIPTION

Nonwoven abrasive wheels, such as unitized abrasive wheels and convoluteabrasive wheels, can be prepared from lofty, fibrous, bonded, nonwovensheets or webs containing super abrasive particles such as diamond orcubic boron nitrate abrasive particles. Such sheets or webs may bemanufactured through processes that include coating a curable binderprecursor, typically in slurry form, on or throughout a nonwoven fibrousweb. In the formation of unitized or convolute abrasive wheels, thenonwoven fiber web is typically compressed (i.e., densified) relative tononwoven fiber webs used in lofty open nonwoven articles.

Nonwoven fiber webs suitable for use are known in the abrasives art.Typically, the nonwoven fiber web comprises an entangled web of fibers.The fibers may comprise continuous fiber, staple fiber, or a combinationthereof. For example, the fiber web may comprise staple fibers having alength of at least about 20 millimeters (mm), at least about 30 mm, orat least about 40 mm, and less than about 110 mm, less than about 85 mm,or less than about 65 mm, although shorter and longer fibers (e.g.,continuous filaments) may also be useful. The fibers may have a finenessor linear density of at least about 1.7 decitex (dtex, i.e., grams/10000meters), at least about 6 dtex, or at least about 17 dtex, and less thanabout 560 dtex, less than about 280 dtex, or less than about 120 dtex,although fibers having lesser and/or greater linear densities may alsobe useful. Mixtures of fibers with differing linear densities may beuseful, for example, to provide an abrasive article that upon use willresult in a specifically preferred surface finish. If a spunbondnonwoven is used, the filaments may be of substantially larger diameter,for example, up to 2 mm or more in diameter.

The fiber web may be made, for example, by conventional air laid,carded, stitch bonded, spun bonded, wet laid, and/or melt blownprocedures. Air laid fiber webs may be prepared using equipment such as,for example, that available under the trade designation RANDO WEBBERfrom Rando Machine Company of Macedon, N.Y.

Nonwoven fiber webs are typically selected to be compatible withadhering binders and abrasive particles while also being compatible withother components of the article, and typically can withstand processingconditions (e.g., temperatures) such as those employed duringapplication and curing of the curable binder precursor. The fibers maybe chosen to affect properties of the abrasive article such as, forexample, flexibility, elasticity, durability or longevity, abrasiveness,and finishing properties. Examples of fibers that may be suitableinclude natural fibers, synthetic fibers, and mixtures of natural and/orsynthetic fibers. Examples of synthetic fibers include those made frompolyester (e.g., polyethylene terephthalate), nylon (e.g., hexamethyleneadipamide, polycaprolactam), polypropylene, acrylonitrile (i.e.,acrylic), rayon, cellulose acetate, polyvinylidene chloride-vinylchloride copolymers, and vinyl chloride-acrylonitrile copolymers.Examples of suitable natural fibers include cotton, wool, jute, andhemp. The fiber may be of virgin material or of recycled or wastematerial, for example, reclaimed from garment cuttings, carpetmanufacturing, fiber manufacturing, or textile processing. The fiber maybe homogenous or a composite such as a bicomponent fiber (e.g., aco-spun sheath-core fiber). The fibers may be tensilized and crimped,but may also be continuous filaments such as those formed by anextrusion process. Combinations of fibers may also be used.

Prior to coating and/or impregnation with a binder precursorcomposition, the nonwoven fiber web typically has a weight per unit area(i.e., basis weight) of at least about 50 grams per square meter (gsm),at least about 100 gsm, or at least about 150 gsm; and/or less thanabout 600 gsm, less than about 500 gsm, or less than about 400 gsm, asmeasured prior to any coating (e.g., with the curable binder precursoror optional pre-bond resin), although greater and lesser basis weightsmay also be used. In addition, prior to impregnation with the curablebinder precursor, the fiber web typically has a thickness of at leastabout 3 mm, at least about 6 mm, or at least about 10 mm; and/or lessthan about 100 mm, less than about 50 mm, or less than about 25 mm,although greater and lesser thicknesses may also be useful.

Frequently, as known in the abrasives art, it is useful to apply aprebond resin to the nonwoven fiber web prior to coating with thecurable binder precursor. The prebond resin serves, for example, to helpmaintain the nonwoven fiber web integrity during handling, and may alsofacilitate bonding of the urethane binder to the nonwoven fiber web.Examples of prebond resins include phenolic resins, urethane resins,hide glue, acrylic resins, urea-formaldehyde resins,melamine-formaldehyde resins, epoxy resins, and combinations thereof.The amount of pre-bond resin used in this manner is typically adjustedtoward the minimum amount consistent with bonding the fibers together attheir points of crossing contact. In those cases, wherein the nonwovenfiber web includes thermally bondable fibers, thermal bonding of thenonwoven fiber web may also be helpful to maintain web integrity duringprocessing.

In those nonwoven abrasive articles including a lofty open nonwovenfiber web (e.g., hand pads, and surface conditioning discs and belts,flap brushes, or nonwoven abrasive webs used to make unitized orconvolute abrasive wheels) many interstices between adjacent fibers thatare substantially unfilled by the binder and abrasive particles,resulting in a composite structure of extremely low density having anetwork on many relatively large intercommunicated voids. The resultinglightweight, lofty, extremely open fibrous construction is essentiallynon-clogging and non-filling in nature, particularly when used inconjunction with liquids such as water and oils. These structures alsocan be readily cleaned upon simple flushing with a cleansing liquid,dried, and left for substantial periods of time, and then reused.Towards these ends, the voids in these nonwoven abrasive articles maymake up at least about 75 percent, and preferably more, of the totalspace occupied by the composite structure.

Examples of suitable curable binder precursors (e.g., suitable for thefirst and/or second curable binder precursor) including resole phenolicresins, novolac phenolic resins, epoxy resins, polymerizable acrylicmonomers oligomers and polymers, alkyd resins, cyanate resins,aminoplast resins, urea-formaldehyde resins, urethane resins (one-partand two-part), and combinations thereof. Depending on the curable binderprecursor system selected, an appropriate curative (e.g., a crosslinker,catalyst, or initiator) may also be present. Selection and amounts ofsuitable such curatives are well known in the abrasives art.

Curable binder compositions may contain various additives. For example,conventional resin filler(s) (e.g., calcium carbonate or fine fibers),lubricant(s) (e.g., alkali metal salts of stearic acid and lightpetroleum oils), grinding aid(s) (e.g., potassium fluoroborate), wettingagent(s) or surfactant(s) (e.g., sodium lauryl sulfate), defoamer(s),pigment(s), dye(s), biocide(s), coupling agent(s) (e.g., organosilanes),plasticizer(s) (e.g., polyalkylene polyols or phthalate esters),thickeners, and combinations thereof. Typically, the curable binderprecursor will include at least one solvent (e.g., isopropyl alcohol,methyl ethyl ketone, water) to facilitate coating of the curable binderprecursor on the nonwoven fiber web, although this is not a requirement.

In some embodiments, the curable binder precursor is a urethaneprepolymer. Examples of useful urethane prepolymers includepolyisocyanates and blocked versions thereof. Typically, blockedpolyisocyanates are substantially unreactive to isocyanate reactivecompounds (e.g., amines, alcohols, thiols) under ambient conditions(e.g., temperatures in a range of from about 20° C. to about 25° C.),but upon application of sufficient thermal energy the blocking agent isreleased, thereby generating isocyanate functionality that reacts withthe amine curative to form a covalent bond.

Useful polyisocyanates include, for example, aliphatic polyisocyanates(e.g., hexamethylene diisocyanate or trimethylhexamethylenediisocyanate); alicyclic polyisocyanates (e.g., hydrogenated xylylenediisocyanate or isophorone diisocyanate); aromatic polyisocyanates(e.g., tolylene diisocyanate or 4,4′-diphenylmethane diisocyanate);adducts of any of the foregoing polyisocyanates with a polyhydricalcohol (e.g., a diol, low molecular weight hydroxyl group-containingpolyester resin, and/or water); adducts of the foregoing polyisocyanates(e.g., isocyanurates, biurets); and mixtures thereof.

Useful commercially available polyisocyanates include, for example,those available under the trade designation ADIPRENE from ChemturaCorporation, Middlebury, Conn. (e.g., ADIPRENE L 0311, ADIPRENE L 100,ADIPRENE L 167, ADIPRENE L 213, ADIPRENE L 315, ADIPRENE L 680, ADIPRENELF 1800A, ADIPRENE LF 600D, ADIPRENE LFP 1950A, ADIPRENE LFP 2950A,ADIPRENE LFP 590D, ADIPRENE LW 520, and ADIPRENE PP 1095);polyisocyanates available under the trade designation MONDUR from BayerCorporation, Pittsburgh, Pa. (e.g., MONDUR 1437, MONDUR MP-095, orMONDUR 448); and polyisocyanates available under the trade designationsAIRTHANE and VERSATHANE from Air Products and Chemicals, Allentown, Pa.(e.g., AIRTHANE APC-504, AIRTHANE PST-95A, AIRTHANE PST-85A, AIRTHANEPET-91A, AIRTHANE PET-75D, VERSATHANE STE-95A, VERSATHANE STE-P95,VERSATHANE STS-55, VERSATHANE SME-90A, and VERSATHANE MS-90A).

To lengthen pot-life, polyisocyanates such as, for example, thosementioned above may be blocked with a blocking agent according tovarious techniques known in the art. Exemplary blocking agents includeketoximes (e.g., 2-butanone oxime); lactams (e.g., epsilon-caprolactam);malonic esters (e.g., dimethyl malonate and diethyl malonate); pyrazoles(e.g., 3,5-dimethylpyrazole); alcohols including tertiary alcohols(e.g., t-butanol or 2,2-dimethylpentanol), phenols (e.g., alkylatedphenols), and mixtures of alcohols as described.

Exemplary useful commercially available blocked polyisocyanates includethose marketed by Chemtura Corporation under the trade designationsADIPRENE BL 11, ADIPRENE BL 16, ADIPRENE BL 31, ADIPRENE BL 46, andADIPRENE BL 500; and blocked polyisocyanates marketed by BaxendenChemicals, Ltd., Accrington, England under the trade designation TRIXENE(e.g., TRIXENE BL 7641, TRIXENE BL 7642, TRIXENE BL 7772, and TRIXENE BL7774).

Typically, the amount of any urethane prepolymer present in the curablebinder precursor is in an amount of from 10 to 40 percent by weight,more typically in an amount of from 15 to 30 percent by weight, and evenmore typically in an amount of from 20 to 25 percent by weight based onthe total weight of the curable binder precursor, although amountsoutside of these ranges may also be used.

Exemplary curatives for urethane prepolymers include aromatic,alkyl-aromatic, or alkyl polyfunctional amines, preferably primaryamines. Examples of useful amine curatives include4,4′-methylenedianiline; polymeric methylene dianilines having afunctionality of 2.1 to 4.0 which include those known under the tradedesignations CURITHANE 103, commercially available from the Dow ChemicalCompany, and MDA-85 from Bayer Corporation, Pittsburgh, Pa.;1,5-diamine-2-methylpentane; tris(2-aminoethyl) amine;3-aminomethyl-3,5,5-trimethylcyclohexylamine (i.e., isophoronediamine),trimethylene glycol di-p-aminobenzoate, bis(o-aminophenylthio)ethane,4,4′-methylenebis(dimethyl anthranilate),bis(4-amino-3-ethylphenyl)methane (e.g., as marketed under the tradedesignation KAYAHARD AA by Nippon Kayaku Company, Ltd., Tokyo, Japan),and bis(4-amino-3,5-diethylphenyl)methane (e.g., as marketed under thetrade designation LONZACURE M-DEA by Lonza, Ltd., Basel, Switzerland),and mixtures thereof. If desired, polyol(s) may be added to the curablebinder precursor, for example, to modify (e.g., to retard) cure rates asrequired by the intended use. The amine curative should be present in anamount effective (i.e., an effective amount) to cure the blockedpolyisocyanate to the degree required by the intended application; forexample, the amine curative may be present in a stoichiometric ratio ofcurative to isocyanate (or blocked isocyanate) in a range of from 0.8 to1.35; for example, in a range of from 0.85 to 1.20, or in a range offrom 0.90 to 0.95, although stoichiometric ratios outside these rangesmay also be used.

One method of making nonwoven abrasive articles according to the presentinvention includes the steps in the following order: applying a prebondcoating to the nonwoven fiber web (e.g., by roll-coating or spraycoating), curing the prebond coating, impregnating the nonwoven fiberweb with a make layer precursor having a first curable binder precursor(e.g., commonly termed a “make coat”, by roll-coating or spray coating),applying abrasive particles to the curable binder precursor, optionallyapplying a second curable binder precursor (which may be the same ordifferent) over the make layer precursor and abrasive particles(commonly termed a “size coat” or “size layer precursor”) and thencuring the curable binder precursor(s).

The amount of curable binder precursor in the make layer precursor (andoptional size layer precursor) should generally be sufficient that theabrasive platelets are firmly adhered to the nonwoven fiber web in thefinished article, but not so great that appreciable amounts of theabrasive platelets (e.g., less than 10 percent, less than 5 percent,less than 2 percent) are deposited on top of other abrasive platelets toform a double layer. In some embodiments, curable binder precursor(s)(excluding any solvent that may be present) is/are preferably coatedonto the nonwoven fiber web in an amount of from 25 to 1000 grams persquare meter (gsm), more preferably 100 to 1000 gsm, and even morepreferably 75 to 750 gsm, although values outside these ranges may alsobe used.

Useful abrasive platelets may be the result of a crushing operation(e.g., crushed abrasive particles that have been sorted for shape andsize) or the result of a shaping operation (i.e., shaped abrasiveplatelets) in which an abrasive precursor material is shaped (e.g.,molded), dried, and converted to ceramic material. Combinations ofabrasive platelets resulting from crushing with abrasive plateletsresulting from a shaping operation may also be used. The abrasiveplatelets may be in the form of, for example, individual particles,agglomerates, composite particles, and mixtures thereof.

The abrasive platelets should have sufficient hardness and surfaceroughness to function as crushed abrasive particles in abradingprocesses. Preferably, the abrasive platelets have a Mohs hardness of atleast 4, at least 5, at least 6, at least 7, or even at least 8.

Crushed abrasive platelets can be obtained from commercial sources, byknown methods, and/or by shape sorting crushed abrasive particles; forexample, using a shape-sorting table as is known in the art.

Suitable abrasive particles (including abrasive platelets and optionallyblocky or needle-shape abrasive particles) that may be included innonwoven abrasive articles according to the present disclosure includecrushed abrasive particles comprising fused aluminum oxide, heat-treatedaluminum oxide, white fused aluminum oxide, ceramic aluminum oxidematerials such as those commercially available as 3M CERAMIC ABRASIVEGRAIN from 3M Company, St. Paul, Minn., brown aluminum oxide, bluealuminum oxide, silicon carbide (including green silicon carbide),titanium diboride, boron carbide, tungsten carbide, garnet, titaniumcarbide, diamond, cubic boron nitride, garnet, fused alumina zirconia,iron oxide, chromia, zirconia, titania, tin oxide, quartz, feldspar,flint, emery, sol-gel-derived ceramic (e.g., alpha alumina), andcombinations thereof. Examples of sol-gel-derived abrasive particlesfrom which the abrasive platelets can be isolated, and methods for theirpreparation can be found, in U.S. Pat. No. 4,314,827 (Leitheiser etal.); U.S. Pat. No. 4,623,364 (Cottringer et al.); U.S. Pat. No.4,744,802 (Schwabel), U.S. Pat. No. 4,770,671 (Monroe et al.); and U.S.Pat. No. 4,881,951 (Monroe et al.). It is also contemplated that theabrasive particles could comprise abrasive agglomerates such, forexample, as those described in U.S. Pat. No. 4,652,275 (Bloecher et al.)or U.S. Pat. No. 4,799,939 (Bloecher et al.). In some embodiments, theabrasive particles may be surface-treated with a coupling agent (e.g.,an organosilane coupling agent) or other physical treatment (e.g., ironoxide or titanium oxide) to enhance adhesion of the crushed abrasiveparticles to the binder. The abrasive particles may be treated beforecombining them with the binder, or they may be surface treated in situby including a coupling agent to the binder.

Preferably, the abrasive particles (and especially the abrasiveplatelets) comprise ceramic abrasive particles such as, for example,sol-gel-derived polycrystalline alpha alumina particles. Ceramicabrasive particles composed of crystallites of alpha alumina, magnesiumalumina spinel, and a rare earth hexagonal aluminate may be preparedusing sol-gel precursor alpha alumina particles according to methodsdescribed in, for example, U.S. Pat. No. 5,213,591 (Celikkaya et al.)and U.S. Publ. Pat. Appln. Nos. 2009/0165394 A1 (Culler et al.) and2009/0169816 A1 (Erickson et al.).

Further details concerning methods of making sol-gel-derived abrasiveparticles can be found in, for example, U.S. Pat. No. 4,314,827(Leitheiser); U.S. Pat. No. 5,152,917 (Pieper et al.); U.S. Pat. No.5,435,816 (Spurgeon et al.); U.S. Pat. No. 5,672,097 (Hoopman et al.);U.S. Pat. No. 5,946,991 (Hoopman et al.); U.S. Pat. No. 5,975,987(Hoopman et al.); and U.S. Pat. No. 6,129,540 (Hoopman et al.); and inU.S. Publ. Pat. Appln. No. 2009/0165394 A1 (Culler et al.).

A majority of the abrasive particles are abrasive platelets. Theabrasive platelets preferably comprise at least 50 weight percent of thetotal weight of abrasive particles included in the nonwoven abrasivearticle, preferably at least 55 weight percent, at least 60 weightpercent, at least 65 weight percent, at least 70 weight percent, atleast 75 weight percent, at least 80 weight percent, at least 85 weightpercent, at least 90 weight percent, at least 95 weight percent, atleast 99 weight percent, or even 100 weight percent, although this isnot a requirement.

In some preferred embodiments, useful abrasive particles (especially inthe case of the abrasive platelets) may be shaped abrasive particles canbe found in U.S. Pat. No. 5,201,916 (Berg); U.S. Pat. No. 5,366,523(Rowenhorst (Re 35,570)); and U.S. Pat. No. 5,984,988 (Berg). U.S. Pat.No. 8,034,137 (Erickson et al.) describes alumina abrasive particlesthat have been formed in a specific shape, then crushed to form shardsthat retain a portion of their original shape features. In someembodiments, shaped alpha alumina particles are precisely-shaped (i.e.,the particles have shapes that are at least partially determined by theshapes of cavities in a production tool used to make them. Detailsconcerning such abrasive particles and methods for their preparation canbe found, for example, in U.S. Pat. No. 8,142,531 (Adefris et al.); U.S.Pat. No. 8,142,891 (Culler et al.); and U.S. Pat. No. 8,142,532(Erickson et al.); and in U.S. Pat. Appl. Publ. Nos. 2012/0227333(Adefris et al.); 2013/0040537 (Schwabel et al.); and 2013/0125477(Adefris).

Surface coatings on the abrasive particles may be used to improve theadhesion between the crushed abrasive particles and a binder in abrasivearticles, or can be used to aid in electrostatic deposition of theabrasive particles. In one embodiment, surface coatings as described inU.S. Pat. No. 5,352,254 (Celikkaya) in an amount of 0.1 to 2 percentsurface coating to abrasive particle weight may be used. Such surfacecoatings are described in U.S. Pat. No. 5,213,591 (Celikkaya et al.);U.S. Pat. No. 5,011,508 (Wald et al.); U.S. Pat. No. 1,910,444(Nicholson); U.S. Pat. No. 3,041,156 (Rowse et al.); U.S. Pat. No.5,009,675 (Kunz et al.); U.S. Pat. No. 5,085,671 (Martin et al.); U.S.Pat. No. 4,997,461 (Markhoff-Matheny et al.); and U.S. Pat. No.5,042,991 (Kunz et al.). Additionally, the surface coating may preventshaped abrasive particles from capping. Capping is the term to describethe phenomenon where metal particles from the workpiece being abradedbecome welded to the tops of the abrasive particles. Surface coatings toperform the above functions are known to those of skill in the art.

The abrasive platelets may be selected to have a length and/or width ina range of from 0.1 micrometers to 3.5 millimeters (mm), more typically0.05 mm to 3.0 mm, and more typically 0.1 mm to 2.6 mm, although otherlengths and widths may also be used.

The abrasive platelets may be selected to have a thickness in a range offrom 0.1 micrometer to 1.6 mm, more typically from 1 micrometer to 1.2mm, although other thicknesses may be used. In some embodiments, plateycrushed abrasive particles may have an aspect ratio (length tothickness) of at least 2, 3, 4, 5, 6, or more.

In some preferred embodiments, the abrasive platelets comprise shapedabrasive platelets bounded by upper and lower surfaces with a pluralityof sidewalls disposed therebetween. Examples include platelets shaped asa truncated triangular prism or truncated triangular pyramid.

Length, width, and thickness of the abrasive platelets can be determinedon an individual or average basis, as desired. Suitable techniques mayinclude inspection and measurement of individual particles, as well asusing automated image analysis techniques (e.g., using a dynamic imageanalyzer such as a CAMSIZER XT image analyzer from Retsch TechnologyGmbh of Haan, Germany) according to test method ISO 13322-2:2006“Particle size analysis—Image analysis methods—Part 2: Dynamic imageanalysis methods”.

Preferably, the abrasive platelets nominally have the same size andshape although this is not a requirement.

Suitable abrasive particles (including abrasive platelets as well asother shapes) may be independently sized according to an abrasivesindustry recognized specified nominal grade. Exemplary abrasive industryrecognized grading standards include those promulgated by ANSI (AmericanNational Standards Institute), FEPA (Federation of European Producers ofAbrasives), and JIS (Japanese Industrial Standard). ANSI gradedesignations (i.e., specified nominal grades) include, for example: ANSI4, ANSI 6, ANSI 8, ANSI 16, ANSI 24, ANSI 36, ANSI 46, ANSI 54, ANSI 60,ANSI 70, ANSI 80, ANSI 90, ANSI 100, ANSI 120, ANSI 150, ANSI 180, ANSI220, ANSI 240, ANSI 280, ANSI 320, ANSI 360, ANSI 400, and ANSI 600.FEPA grade designations include F4, F5, F6, F7, F8, F10, F12, F14, F16,F16, F20, F22, F24, F30, F36, F40, F46, F54, F60, F70, F80, F90, F100,F120, F150, F180, F220, F230, F240, F280, F320, F360, F400, F500, F600,F800, F1000, F1200, F1500, and F2000. JIS grade designations include1158, 11512, JIS16, JIS24, JIS36, JIS46, JIS54, 11560, 11580, JIS100,JIS150, JIS180, JIS220, JIS240, JIS280, JIS320, JIS360, JIS400, JIS600,JIS800, JIS1000, 1151500, JIS2500, 1154000, JIS6000, JIS8000, andJIS10,000

Alternatively, the crushed abrasive particles can be graded to a nominalscreened grade using U.S.A. Standard Test Sieves conforming to ASTM E-11“Standard Specification for Wire Cloth and Sieves for Testing Purposes”.ASTM E-11 prescribes the requirements for the design and construction oftesting sieves using a medium of woven wire cloth mounted in a frame forthe classification of materials according to a designated particle size.A typical designation may be represented as −18+20 meaning that thecrushed abrasive particles pass through a test sieve meeting ASTM E-11specifications for the number 18 sieve and are retained on a test sievemeeting ASTM E-11 specifications for the number 20 sieve. In oneembodiment, the crushed abrasive particles have a particle size suchthat most of the particles pass through an 18 mesh test sieve and can beretained on a 20, 25, 30, 35, 40, 45, or 50 mesh test sieve. In variousembodiments, the crushed abrasive particles can have a nominal screenedgrade of: −18+20, −20/+25, −25+30, −30+35, −35+40, 5−40+45, −45+50,−50+60, −60+70, −70/+80, −80+100, −100+120, −120+140, −140+170,−170+200, −200+230, −230+270, −270+325, −325+400, −400+450, −450+500, or−500+635. Alternatively, a custom mesh size can be used such as −90+100.

Typically, the coating weight for the abrasive particles (independent ofother ingredients in the curable binder precursor) may depend, forexample, on the particular binder used, the process for applying theabrasive particles, and the size of the abrasive particles. For example,the coating weight of the abrasive particles on the nonwoven fiber web(before any compression) may be at least 100 grams per square meter(gsm), at least 600 gsm, or at least 800 gsm; and/or less than 3000 gsm,less than about 2000 gsm, or less than about 1000 gsm, although greateror lesser coating weights may be also be used. Electrostatic coating isused to apply the abrasive platelets to the make coat-treated nonwovenfiber web. During electrostatic coating, electrostatic charges areapplied to the abrasive particles and this creates a difference inpotential between the particles and nonwoven web which is electricallygrounded. The difference in potential attracts the abrasive particles tothe nonwoven web. Electrostatic coating tends to orient the abrasiveparticles, which tends to lead to better abrading performance.

One useful electrostatic coating apparatus has a conveyor belt movingthrough an electrostatic field. A coater applies a make layer precursorcoating onto the nonwoven fiber web, which follows a web path guidingthe nonwoven through the electrostatic field above the conveyor belt. Aparticle feeder applies the abrasive particles to form a layer ofabrasive particles on the conveyor belt. As the conveyor belt moves theparticle layer through the electrostatic field, abrasive particles aretransferred upward to the make layer precursor-coated nonwoven fiber webfrom the conveyor belt. Further details concerning this type of particlecoating process as applied to manufacture of a coated abrasive articlecan be found in, U.S. Pat. No. 8,869,740 B2 (Moren et al.), except thata nonwoven fiber web should be substituted for the backing.

The resulting construction is exposed to conditions sufficient tosolidify the make layer precursor. Details concerning voltages anddeposition rates for specific binder precursor-coated nonwoven fiberwebs can be readily determined by those of skill in the art.Electrostatic coating may be carried out toward one or both sides of thebinder precursor-coated nonwoven fiber web. Other methods ofelectrostatic coating may also be used such as projecting particlestowards the nonwoven web using normal spraying methods, and thenorienting the particles on the fibers by an applied electrostaticcharge.

At this point a size layer precursor may optionally be applied over atleast a portion of the make layer precursor and abrasive particles(e.g., abrasive platelets) platelets. The size layer precursor comprisesa second curable binder precursor which may be the same as, or differentfrom, the make layer precursor. Any material used in the make layerprecursor may also be used in the size layer precursor, for example.Likewise, process conditions for the make layer precursor may also beused to coat and cure the size layer precursor to form a size layerdisposed on at least a portion of the make layer and abrasive particles.The resulting construction is exposed to conditions sufficient tosolidify the size layer precursor.

As a result of the electrostatic coating process, typically incombination with controlling the amount of binder precursor to avoidexcess, the abrasive platelets can be oriented such that they areorthogonal to the respective at least one fiber to which they arebonded. Moreover, the abrasive platelets can be arranged, in at leastsome embodiments, such that they are substantially orthogonal to atleast one fiber to which it is bonded (i.e., forming an angle with thefiber of from 70 to 110 degrees, preferably 80 to 100 degrees).

The present inventors have found that conventional electrosprayprocesses are generally inefficient for practicing the presentdisclosure.

An exemplary embodiment of a nonwoven abrasive article 100 is shown inFIGS. 1A and 1B. Lofty open low-density fibrous web 110 is formed ofentangled filaments 115 held together by binder 120. Abrasive platelets140 are secured to fibrous web 110 on exposed surfaces of filaments 115by binder 120. A majority of abrasive platelets 140 are orientedorthogonal to at least one fiber to which it is bonded resulting incutting points 150 being outwardly oriented relative to the fiber.

Convolute abrasive wheels may be made, for example, by winding thenonwoven fiber web, after the size layer precursor has been applied tothe make layer and abrasive particles and partially cured, under tensionaround a core member (e.g., a tubular or rod-shaped core member) suchthat the impregnated nonwoven fiber layers become compressed, and thenfully curing the size layer precursor. A convolute abrasive wheel 200 isshown in FIG. 2, wherein nonwoven fiber web 210 is coated with a binderthat secures the abrasive particles (e.g., as in FIGS. 1A and 1B) to thelayered nonwoven fiber web and binds layers of the layered nonwovenfiber web 210 to each other. The nonwoven fiber web 210 is spirallydisposed around and affixed to core member 230. If desired, convoluteabrasive wheels may be dressed prior to use to remove surfaceirregularities, for example, using methods known in the abrasive arts.

Similarly, unitized abrasive wheels can be made, for example, as withconvolute wheels, except that instead of winding the size layerprecursor coated web, it is stacked and compressed prior to curing. Aunitized nonwoven abrasive wheel 300 is shown in FIG. 3 having aplurality of nonwoven abrasive layers 310, which have been compressedand cured. After curing the curable binder precursor, the resultingfused slab can be die cut to form the abrasive wheel having a centralhole 320.

When compressing the layers of impregnated nonwoven fiber web in makingan abrasive wheel, the one or more layers are typically compressed toform a slab having a density that is from 1 to 10 times that of thedensity of the layers in their non-compressed state. The slab is thentypically subjected to heat molding (e.g., for from 2 to 20 hours) atelevated temperature (e.g., at 135° C.), typically depending on thecurable binder precursor selected and slab/bun size.

In addition to the foregoing abrasive wheels, methods of making nonwovenabrasive articles according to the present disclosure are useful forpreparing hand pads, floor pads, flap brushes, surface conditioningpads, discs, and belts, for example.

Further details concerning nonwoven abrasive articles, abrasive wheelsand methods for their manufacture may be found, for example, in U.S.Pat. No. 2,958,593 (Hoover et al.); U.S. Pat. No. 5,591,239 (Larson etal.); U.S. Pat. No. 6,017,831 (Beardsley et al.); and in U.S. Pat. Appl.Publ. 2006/0041065 A 1 (Barber, Jr.).

Select Embodiments of the Present Disclosure

In a first embodiment, the present disclosure provides a nonwovenabrasive article comprising:

a lofty open nonwoven fiber web comprising entangled fibers; and

abrasive platelets secured to the entangled fibers by at least onebinder material, and

wherein a majority of the abrasive platelets are respectively bonded inan edge-wise manner to at least one of the entangled fibers,respectively.

In a second embodiment, the present disclosure provides a nonwovenabrasive article according to the first embodiment, wherein the abrasiveplatelets comprise triangular shaped abrasive platelets.

In a third embodiment, the present disclosure provides a nonwovenabrasive article according to the first or second embodiment, whereinthe abrasive platelets are closely-packed along the lengths of theentangled fibers.

In a fourth embodiment, the present disclosure provides a nonwovenabrasive article according to any one of the first to third embodiments,wherein the nonwoven abrasive article comprises: a hand pad; a floorpad; flap brush; or a surface conditioning pad, disc, or belt.

In a fifth embodiment, the present disclosure provides a nonwovenabrasive article according to any one of the first to fourthembodiments, wherein the abrasive platelets nominally have the same sizeand shape.

In a sixth embodiment, the present disclosure provides a nonwovenabrasive article according to any one of the first to fifth embodiments,wherein a majority of the abrasive platelets are arranged such that theyare orthogonal to the entangled fibers to which they are bonded.

In a seventh embodiment, the present disclosure provides a nonwovenabrasive article according to any one of the first to sixth embodiments,wherein the abrasive platelets comprise shaped abrasive plateletsbounded by upper and lower surfaces and a plurality of sidewallsdisposed therebetween.

In an eighth embodiment, the present disclosure provides a convolutenonwoven abrasive wheel comprising a spirally wound and compressednonwoven abrasive article according to any one of the first to seventhembodiments.

In a ninth embodiment, the present disclosure provides a method ofmaking an abrasive article, comprising the steps:

i) providing a lofty open nonwoven fiber web comprising a plurality ofentangled fibers;

ii) coating at least a portion of the lofty open nonwoven fiber web witha first curable binder precursor to provide a coated fiber web;

iii) electrostatically depositing a plurality of abrasive platelets onat least a portion of the first curable binder precursor; and

iv) at least partially curing the first curable binder,

wherein a majority of the abrasive platelets are each bonded in anedge-wise manner to at least one of the entangled fibers, respectively.

In a tenth embodiment, the present disclosure provides a methodaccording to the ninth embodiment, further comprising coating at least aportion of the first curable binder precursor and abrasive plateletswith a second curable binder precursor, and at least partially curingthe second binder precursor.

In an eleventh embodiment, the present disclosure provides a methodaccording to the ninth or tenth embodiment, further comprisingconverting the nonwoven abrasive web into at least one of at least onehand pad; at least one floor pad; at least one flap brush; or at leastone surface conditioning pad, disc, or belt.

In a twelfth embodiment, the present disclosure provides a methodaccording to the ninth or tenth embodiment, further comprising;

v) converting the nonwoven abrasive article into at least one of aconvolute abrasive wheel or unitized abrasive wheel.

In a thirteenth embodiment, the present disclosure provides a methodaccording to any one of the ninth to twelfth embodiments, wherein theabrasive platelets comprise triangular shaped abrasive platelets.

In a fourteenth embodiment, the present disclosure provides a methodaccording to any one of the ninth to thirteenth embodiments, wherein theabrasive platelets are closely-packed along the lengths of the entangledfibers.

In a fifteenth embodiment, the present disclosure provides a methodaccording to any one of the ninth to fourteenth embodiments, wherein amajority of the abrasive platelets are arranged such that they areorthogonal to the entangled fibers to which they are bonded.

In a sixteenth embodiment, the present disclosure provides a methodaccording to any one of the ninth to fifteenth embodiments, wherein theabrasive platelets comprise shaped abrasive platelets.

Objects and advantages of this disclosure are further illustrated by thefollowing non-limiting examples, but the particular materials andamounts thereof recited in these examples, as well as other conditionsand details, should not be construed to unduly limit this disclosure.

EXAMPLES

Unless otherwise noted, all parts, percentages, ratios, etc. in theExamples and the rest of the specification are by weight.

Materials

TABLE 1 ABBRE- VIA- TION DESCRIPTION A1 acrylic resin emulsion, obtainedas RHOPLEX TR-407 from Rohm and Haas Co., Philadelphia, Pennsylvania A2acrylic resin emulsion, obtained as RHOPLEX GL-720 from Rohm and HaasCo. WU waterborne polyurethane dispersion, obtained as WITCOBOND W-290Hfrom Chemtura Corp., Middlebury, Connecticut PU1 blocked urethaneprepolymer, obtained as ADIPRENE BL46 from Chemtura Corp. PU2 blockedurethane prepolymer, obtained as ADIPRENE BLM500 from Chemtura Corp. PU3blocked urethane prepolymer, obtained as ADIPRENE BL16 from ChemturaCorp. CUR aromatic amine curative, obtained as LAPOX AH664 from AtulAmericas Inc., Charlotte, North Carolina CUR2 aromatic amine curative,obtained as LAPOX K-450 from Atul Americas Inc. PR phenolic resin,obtained as ARCLIN 80 5077A from Arclin Inc, Atlanta ,Georgia POLpolyol, obtained as ARCOL LG-650 from Bayer MaterialScience, Ltd,Pittsburgh, Pennsylvania DYN nonionic surfactant, obtained as DYNOL 604from Air Products and Chemicals, Inc., Allentown, Pennsylvania ER1 epoxynovolac resin, obtained as DEN 438 from Dow Chemical Co., Midland,Michigan KBF4 micropulverized potassium fluoroborate from Atotech USA,Rock Hill, South Carolina PMA propylene glycol monomethyl ether acetate,obtained as DOWANOL PMA from Dow Chemical Co. LiSt lithium stearate,obtained as LIC 17 from Baerlocher USA, Cincinnati, Ohio SILICAamorphous silica, obtained as SYLISIA 356 from Fuji Sylisia ChemicalLtd., Research Triangle Park, North Carolina PEG polyethylene glycol,obtained as PEG 6000 DS from The Hallstar Co., Chicago, Illinois CaStcalcium silicate, obtained as WOLLASTOCOAT 10072 from NYCO Minerals,Willsboro, New York ER2 white epoxy resin, obtained from FerroCorporation, Edison, New Jersey UVA UV absorber, obtained as TINUVIN5151 from Ciba Specialty Chemical Corporation, Tarrytown, New York SAP1Triangular ceramic alumina particle that passes through a 40- mesh sieveand is retained upon a 50-mesh sieve, which gives an average particlesize of 0.014 in (0.36 mm). SAP2 Triangular ceramic alumina particlethat passes through a 70- mesh sieve and is retained upon a 80-meshsieve, which gives an average particle size of 0.008 in (0.20 mm). BlackBlack Colorant, obtained as 1991 B BLACK, from EPS, Marengo, IL. GreenGreen Colorant, obtained as D PHTHALO GREEN, from EPS, Marengo, IL. DFDefoamer, obtained as DAPRO DF 880, from Elementis, Hightstown, NJ. PMEpropylene glycol monomethyl ether, obtained as DOWANOL PM from DowChemical Company, Midland, Michigan CA Curing agent, obtained asEPI-CURE 3105 from Momentive Specialty Chemicals, Inc., Columbus, OhioAL Petroleum oil, obtained as Ace Filter Oil 23N from LubricationTechnologies, Inc., Golden Valley, Minnesota BC Bentonite clay, obtainedas Volclay 325 from American Colloid Company, Arlington Heights,Illinois MIN Aluminum oxide mineral, obtained as Duralum Brown AluminumOxide, Grade 100/150 from Washington Mills Electro Minerals Corporation,Niagara Falls, New York

Orientation Test

Three 100× photomicrographs are taken of representative areas of thesurface of the particle-coated web. The photomicrographs are theninspected to determine the qualitative orientation of the particles withrespect to the fibers of the web. A particle is counted as radiallyoriented if it is bound to the fiber surface by a point or an edge. Aparticle is counted as tangentially oriented if it is bound to the fibersurface on a major face. In addition, at the attachment point of eachparticle, the distance from the center of the fiber to the distal end ofthe particle is measured.

Wheel Abrasion Test

A 6 in. (15.24 cm) diameter 0.5 in. (1.27 cm) thick test wheel ismounted on the spindle of a stationary Baldor three horsepower motor. A2.0 in. (5.08 cm) diameter by 0.125 in. (3.175 mm) thick stainless steeltube workpiece is mounted onto a Slo-Syn single phase synchronous motor(SS700) that is attached to a moveable carriage. The workpiece is set torotate around its longitudinal axis at 32 rpm using the Slo-Syn motor,and the abrasive wheel is set to rotate at 3450 rpm using the Baldormotor. The end of the workpiece is urged against the circumferenceabrasive wheel at selectable loads of either 8 lb (3.6 kg) or 10 lb (4.5kg) while being rotated around its longitudinal axis. During the test,the end of the pre-weighed rotating tube is urged against thepre-weighed wheel at the selected test load for 15-second intervalsfollowed by a noncontact period of 15 seconds. Each Abrasion Test runsfor a total of 30 minutes with the total time the workpiece contactedthe wheel being 15 minutes. Total Cut is determined by the weight lossof the workpiece and the Wheel Wear is determined by the weight loss ofthe abrasive wheel. Results are reported as Cut and Wear in grams foreach test wheel at each test load.

Disc Abrasion Test

A 3 in. (7.62 cm) diameter nonwoven abrasive disc to be tested ismounted on an 3 horsepower, electric servo motor that is disposed overan X-Y table having a 1018 carbon steel panel measuring 6 in.×14 in.×½in. (150 mm×360 mm×13 mm) secured to the X-Y table. The rotary tool isthen activated to rotate at 9000 rpm under no load. The abrasive articleis then urged at an angle of 5 degrees against the panel at a load of 3lbs (1.4 kg). The tool is then set to traverse a 12.53 in. (318.3 mm)path at a rate of 4.7 inches/second (120 mm/sec) in the −X direction;followed by a 0.290 in. (7.35 mm) path in the −Y direction at a rate of14.0 inches/second (356 mm/sec); followed by a 12.53 in. (318.3 mm) pathat a rate of 4.7 in./second (120 mm/sec) in the +X direction; followedby a 0.290 in. (7.35 mm) path in the −Y direction at a rate of 14.00inches/second (355.6 mm/sec). This sequence is repeated 10 times for atotal of 20 passes in the X direction. Twenty such passes along thelength of the panel are completed in each cycle for a total of 8 cycles.The mass of the panel is measured before and after each cycle and addedtogether to calculate a cumulative mass loss (cut) at the end of 8cycles. The disc is weighed before and after the completion of the test(8 cycles) to determine the wear. The number of samples tested for eachexample is reported in Table 3.

Preparation of Nonwoven Prebond Web

A nonwoven web was formed on an air laid fiber web forming machineavailable under the trade designation RANDO-WEBBER from the RandoMachine Corporation of Macedon, N.Y. The fiber web was formed from 25%64 dtex (58 d) nylon 6,6 fiber and 75% 78 dtex (70 d) nylon 6 fiber. Theweight of the web was approximately 415 grams per square meter (gsm) (99grains/24 sq. in.) The nonwoven web was secured to a woven scrim (16×16plain weave nylon STYLE 6713531, Highland Industries, Inc., Greensboro,N.C.) by needle tacking. The web was conveyed to a two-roll coater wherea pre-bond resin was applied at a dry add-on weight of 586 gsm (140grain/24 sq. in.). The pre-bond resin had the following composition (allpercentages relative to component weight): 54.1% PU3, 19.9% CUR2 and 26%PMA. The pre-bond resin was cured to a non-tacky condition by passingthe coated web through a convection oven at 330° F. (166° C.) for 4.5minutes, yielding a pre-bonded, nonwoven web composite of approximately5.8 mm thickness and having a basis weight of 1147 gsm (274 grains/24sq. in.).

Comparative Example A

Onto the prebond described above, an adhesive consisting of 51% PR,46.8% water, 2.1% POL and 0.1% DYN was sprayed to a 210 gsm wet add-on.402 gsm of SAP1 abrasive particles was then applied to the wet coatingby drop coating. The particle coated web was then heated in a convectionoven for 15 minutes at 88° C. (190° F.), 15 minutes at 107° C. (225°F.), and finally 15 minutes at 163° C. (325° F.). The resultingcomposite was evaluated by the Orientation Test. Three replicates wereprepared. Orientation Test results are reported in Tables 2 and 3.

Comparative Example B

Comparative Example B was made identically to Comparative Example A,except that the adhesive was sprayed to a 420 gsm wet add-on.Orientation Test results are reported in Tables 2 and 3.

Example 1

Example 1 was made identically to Comparative Example A, except that theabrasive particles were applied by electrostatic coating. The particleswere placed in contact with a plate which was then charged to anelectric potential of 11 kV. The particles were electrostaticallytransferred against gravity to the adhesive coated surface of the webthat was attached to a grounded plate. The particles traveled verticallyunder the force of the electrostatic field and were deposited andradially oriented onto individual fibers of the nonwoven web.Orientation Test results are reported in Tables 2 and 3.

Example 2

Example 2 was made identically to Example 1, except that 50% of theabrasive particles were applied by drop coating (first) and 50%subsequently coated electrostatically. Orientation Test results arereported in Tables 2 and 3.

TABLE 2 % OF ABRASIVE NUMBER OF PARTICLES PARTICLES GROUP REFERENCEPARTICLES RADIALLY- RADIALLY- AVERAGE, EXAMPLE FIG. STUDIED ORIENTEDORIENTED % Comp. Ex. A-1 FIG. 4 19 6 32 38.8 Comp. Ex. A-2 FIG. 5 22 732 Comp. Ex. A-3 FIG. 6 26 13 50 1a FIG. 7 33 25 76 77.1 1b FIG. 8 34 2574 1c FIG. 9 38 31 82 2a FIG. 10 33 22 67 62.7 2b FIG. 11 21 11 52 2cFIG. 12 29 19 66 Comp. Ex. B-1 FIG. 13 38 20 53 36.4 Comp. Ex. B-2 FIG.14 25 2 8 Comp Ex. B-3 FIG. 15 36 14 39

TABLE 3 FIVE FIVE AVERAGE AVERAGE PARTICLES PARTICLES RADIAL TANGENTIALIN PLANE IN PLANE (GREEN CIRCLES) (RED SQUARES) RADIAL TANGENTIALREFERENCE DISTANCE, DISTANCE, DISTANCE, DISTANCE, EXAMPLE FIG.micrometers micrometers micrometers micrometers Comp. Ex. A-1 FIG. 4 241155 248 135 Comp. Ex. A-2 FIG. 5 Comp. Ex. A-3 FIG. 6 1a FIG. 7 216 169255 136 1b FIG. 8 1c FIG. 9 2a FIG. 10 225 145 267 158 2b FIG. 11 2cFIG. 12 Comp. Ex. B-1 FIG. 13 Not Not Not Not Comp. Ex. B-2 FIG. 14Measured Measured Measured Measured Comp Ex. B-3 FIG. 15

Comparative Example C and Examples 3-4 Abrasive Discs

A size coat consisting of 21.4 wt. % of PR, 13.2 wt. % of PME, 4.6 wt. %of CA, 2.5 wt. % of AL, 0.9 wt. % of BC and 57.4 wt. % of MIN wassprayed to achieve a wet add-on of 741 gsm (177 grains/24 sq. in.) onComparative Example A and Examples 1 and 2, which were then cured at163° C. for 15 minutes. The abrasive discs were identified asComparative Example C and Examples 3 and 4 respectively. The resultingcomposite was evaluated by the Disc Abrasion Test. Two replicates wereprepared. Test results are reported in Table 4, below.

TABLE 4 DISC CUT, DISC WEAR, EXAMPLE grams % weight loss Comp. Ex. C-16.00 2.34 Comp. Ex. C-2 6.59 2.17 3a 9.42 3.97 3b 8.42 3.74 4a 7.32 2.174b 9.36 2.50

As shown in Tables 2 and 3, orientation of the particles withelectrostatic coating was greater than drop coating comparingComparative Example A and Example 1. Example 2 shows an amount oforientation between drop coating and electrostatic coating by applyinghalf the particles by each method. Comparative Example B shows how thebenefit of orientation percent can be affected by increasing the resinadd-on level which allows the particles to fall over on the fiber due toa large amount of coating. Table 4 shows the corresponding disc cutperformance on carbon steel. The increased orientation seen in Examples3 and 4 over Comparative C translates to increased cut for the discs.

Examples 5-6 and Comparative Examples D-E

Unitized nonwoven abrasive wheels and convolute nonwoven abrasive wheelswere made with and without the use of electrostatic spray. The dry spraymineral process uses only air to propel the abrasive particle onto theweb. The electrostatic process also uses air to propel the abrasive butalso imparts an electrical charge onto the particle via an electrode atthe exit tip of the gun (obtained as EASY SELECT MANUAL POWDER GUN USINGA GEMA VOLSTATIC CONTROL BOX from Gema USA, Inc., Indianapolis, Ind.).

Example 5 and Comparative Example D

The unitized abrasive wheel of Example 5 was prepared by spray coating a119 g/m² 24 denier nylon fiber air laid nonwoven web with 30 g/m² (dry)of an acrylic/urethane binder consisting of 38.9 parts A1, 35.86 partswater, 21.51 parts WU, 3.07 parts A2, 0.39 parts Green, 0.26 partsBlack, 0.0002 parts DF following by heating at 285 degrees Fahrenheitfor 6 minutes. 174 g/m² (dry) of a make coating consisting of 57.8 partsPU1, 12.14 parts CUR, 2.89 parts ER1, 15.03 parts KBF4, 5.78 parts PMA,2.89 parts LiSt, 2.31 parts SILICA, and 1.16 parts PEG was then appliedby roll coating. 593 g/m² of SAP2 was then applied by electrostaticspray followed by heating at 300 degrees Fahrenheit for 5 minutes. 474g/m2 (dry) of a size resin consisting of 55.59 parts PU2, 7.73 partsCUR, 2.78 parts ER1, 22.79 parts PMA, 3.34 parts LiSt, 1.95 partsSILICA, 1.11 parts PEG, 3.34 parts CaSt, 0.56 parts ER2, and 0.83 partsUVA was then applied by a roll coater. 8 layers of the resultingabrasive composition were stacked and placed into a mold and compressedto a thickness of 0.5 in (1.27 cm). The mold was placed into an oven at240 degrees Fahrenheit for 6 hours, and after removal the resultingabrasive slab was cut to a 6 in (15.24 cm) diameter unitized wheel offinal density 12 g/in³ (0.74 g/cm³).

Comparative Example D was made identically to Example 5 with theexception that the SAP2 was applied by air spray instead ofelectrostatic spray.

Example 6 and Comparative Example E

Example 6 was prepared identically to Example 5, with the exception thatthe abrasive web composition was converted into a convolute wheel bywinding 432 inches (11 m) around a 1 in (2.54 cm) diameter phenolic coreunder sufficient tension to create a 6 in (15.24 cm) diameter wheel offinal density 12 g/in³ (0.74 g/cm³).

Comparative Example E was prepared identically to Example 6 with theexception that the SAP2 was applied by air spray instead ofelectrostatic spray.

Performance was measured using the Wheel Abrasion Test described above.The test results are shown in Table 5. The resulting cut for ComparativeExample D was 1.3× higher in cut for the 8 lb test 1.7× higher in cutfor the 10 lb test vs. Example 5. The results for Example 6 was 1.6×higher in cut for the 8 lb test and 1.2× higher in cut for the 10 lbtest vs. Comparative Example E. Photos showed the tip of the SAP2 in theunitized construction orientated to the stainless steel workpiece whenapplied using the dry mineral sprayer and the tip of the SAP2 for theconvolute construction is oriented to the workpiece when applied withthe electrostatic process.

TABLE 5 Particle 8 lb test 10 lb test Coating Cut, Wear, Cut, Wear,EXAMPLE Method grams grams grams grams Comp. Ex. D air spray 21 2 36 5 5electrostatic 16 1 21 1 Comp. Ex. E air spray 11 1 27 3 6 electrostatic18 1 33 3

All cited references, patents, and patent applications in the aboveapplication for letters patent are herein incorporated by reference intheir entirety in a consistent manner. In the event of inconsistenciesor contradictions between portions of the incorporated references andthis application, the information in the preceding description shallcontrol. The preceding description, given in order to enable one ofordinary skill in the art to practice the claimed disclosure, is not tobe construed as limiting the scope of the disclosure, which is definedby the claims and all equivalents thereto.

What is claimed is:
 1. A nonwoven abrasive article comprising: a loftyopen nonwoven fiber web comprising entangled fibers; and abrasiveplatelets secured to the entangled fibers by at least one bindermaterial, and wherein a majority of the abrasive platelets arerespectively bonded in an edge-wise manner to at least one of theentangled fibers, respectively.
 2. A nonwoven abrasive article accordingto claim 1, wherein the abrasive platelets comprise triangular shapedabrasive platelets.
 3. A nonwoven abrasive article according to claim 1,wherein the abrasive platelets are closely-packed along the lengths ofthe entangled fibers.
 4. A nonwoven abrasive article according to claim1, wherein the nonwoven abrasive article comprises: a hand pad; a floorpad; or a surface conditioning pad, disc, or belt.
 5. A nonwovenabrasive article according to claim 1, wherein the abrasive plateletsnominally have the same size and shape.
 6. A nonwoven abrasive articleaccording to claim 1, wherein a majority of the abrasive platelets arearranged such that they are orthogonal to the entangled fibers to whichthey are bonded.
 7. A nonwoven abrasive article according to claim 1,wherein the abrasive platelets comprise shaped abrasive plateletsbounded by upper and lower surfaces and a plurality of sidewallsdisposed therebetween.
 8. A convolute nonwoven abrasive wheel comprisinga spirally wound and compressed nonwoven abrasive article according toclaim
 1. 9. A method of making a nonwoven abrasive article, comprisingthe steps: i) providing a lofty open nonwoven fiber web comprising aplurality of entangled fibers; ii) coating at least a portion of thelofty open nonwoven fiber web with a first curable binder precursor toprovide a coated fiber web; iii) electrostatically depositing aplurality of abrasive platelets on at least a portion of the firstcurable binder precursor; and iv) at least partially curing the firstcurable binder precursor, wherein a majority of the abrasive plateletsare each bonded in an edge-wise manner to at least one of the entangledfibers, respectively.
 10. A method according to claim 9, furthercomprising coating at least a portion of the first curable binderprecursor and abrasive platelets with a second curable binder precursor,and at least partially curing the second binder precursor.
 11. A methodaccording to claim 9, further comprising converting the nonwovenabrasive article into at least one of at least one hand pad; at leastone floor pad; or at least one surface conditioning pad, disc, or belt.12. A method according to claim 9, further comprising; v) converting thenonwoven abrasive article into at least one of a convolute abrasivewheel or unitized abrasive wheel.
 13. A method according to claim 9,wherein the abrasive platelets comprise triangular shaped abrasiveplatelets.
 14. A method according to claim 9, wherein the abrasiveplatelets are closely-packed along the lengths of the entangled fibers.15. A method according to claim 9, wherein the abrasive plateletscomprise shaped abrasive platelets.
 16. A nonwoven abrasive articlecomprising: a lofty open nonwoven fiber web comprising entangled fibers;and abrasive platelets secured to the entangled fibers by at least onebinder material, wherein each of the abrasive platelets comprises acutting point opposite a bonding face, wherein the bonding face is athinnest face of the abrasive platelet; and wherein a majority of theabrasive platelets are each respectively bonded to at least one of theentangled fibers such that each of the majority of the abrasiveplatelets is bonded to one of the entangled fibers along the bondingface such that the cutting point is facing away from the entangledfiber, and wherein the bonding face is bonded directly to the entangledfiber.
 17. The nonwoven abrasive article of claim 16, wherein each ofthe abrasive platelets comprises a first polygonal surface and a secondpolygonal surface, and wherein the bonding face comprises a thicknessbetween the first and second polygonal surfaces.
 18. The nonwovenabrasive article of claim 17, wherein the first and second polygonalfaces are substantially congruent and substantially parallel to eachother.
 19. The nonwoven abrasive article of claim 16, wherein thecutting point comprises a vertex of a polygonal face, and the bondingface is partially defined by side of the polygonal face.